The accompanying data on x $=$ head circumference z score $($a comparison score with peers of the same age $-$ a positive score suggests a larger size than for peers$)$ at age $6$ to $14$ months and y $=$ volume of cerebral grey matter $($in ml$)$ at age $2$ to $5$ years were read from a graph in an article.

Cerebral Grey

Matter $($ml$)2-5$ yr Head Circumfer$-$

ence z Scores at

$6-14$ Months

$680-0\mathrm{.}72$

$6901\mathrm{.}8$

$700-0\mathrm{.}27$

$7200\mathrm{.}28$

$7400\mathrm{.}33$

$7402\mathrm{.}1$

$7501\mathrm{.}7$

$7502\mathrm{.}6$

$7601\mathrm{.}7$

$7801\mathrm{.}7$

$7902\mathrm{.}6$

$8102\mathrm{.}7$

$8153\mathrm{.}4$

$8202\mathrm{.}8$

$8250\mathrm{.}93$

$8352\mathrm{.}95$

$8402\mathrm{.}9$

$8452\mathrm{.}8$

$($a$)$ What is the value of the correlation coefficient? $($Give the answer to two decimal places.$)$

r $=$

$($b$)$ Find the equation of the least$-$squares line. $($Give the answer to two decimal places.$)$

y hat $=$

$($c$)$ Predict the volume of cerebral grey matter for a child whose head circumference z score at age $12$ months was $1\mathrm{.}9.($Give the answer to two decimal places.$)$